1. Field of the Invention
The present invention relates to a photometric device for a pseudo format camera capable of performing trimming photography.
2. Related Background Art
A new principle of telescopic photography, a so-called pseudo format camera, has been proposed. As described in U.S. Pat. Nos. 4,650,304, 4,652,104, 4,647,170, etc., a portion (central portion) of a negative film is designated before photography, and is enlarged during printing without using a telescopic lens, so that there is little difference between a printed image obtained by this method and one obtained using a telescopic lens. In the following description, photography according to this principle will be referred to as trimming photography.
A pseudo format camera poses a photometric problem. In the pseudo format camera, a photometric method is not particularly changed between a normal photographing mode and a trimming photographing mode, and a photometric value is obtained from the luminance of the entire region of a field in both the modes.
Therefore, in the normal photographing mode, there is no problem. However, in the trimming photographing mode, if a high-luminance object (e.g., sun) or low-luminance object (e.g., ground) is present outside an enlarged printing region, appropriate exposure cannot be provided to an object region.
In order to solve the above problem, Japanese Patent Laid-Open Applications (Kokai) Nos. 62-50737 and 62-112139 have been proposed. In the former improved proposal, a photometric field angle (fixed) in a photometric optical system in a photometric means is set to be smaller than a photographic field angle of a trimming range when trimming photography is performed. Thus, an exposure error is suppressed in the trimming photographing mode. In the latter proposal, a lens in a photometric optical system is drive-controlled to be capable of focusing. Thus, in the trimming photographing mode, a photometric field angle is decreased compared to that in the normal photographing mode, so that exposure error is suppressed in both the normal and trimming photographing modes.
As another principle, U.S. Pat. No. 4,639,111 has also been proposed. In this proposal, a mask member with a variable mask region is arranged in front (in an optical sense) of a sensor in a photometric means. In the trimming photographing mode, the mask region of the mask member is varied in correspondence with the setting of a trimming range, so that an exposure error is suppressed in both the normal and trimming photographing modes.